Die for hammering sheet metal



. UNITED STATES PATENT OFFICE.

ISAAC E. CRAIG, OF CAMDEN, OHIO.

DIE FOR HAMMERING SHEET METAL.

SPECIFICATION forming part of Letters Patent No. 403,918, dated May 28, 1889.

Application filed December 10, 1888. Serial No. 293,175. (No model.)

To all whom, it may concern.-

Be it known that I, ISAAC E. CRAIG, a citizen of the United States, residing at Camden, in the county of Preble and State of Ohio, have invented a new and useful Improvement in the Manufacture of Polished Sheet-Iron, of which the following is a specification.

My invention relates to the mode of shaping the operative faces of the hammer-dies used in polishing sheet-iron in packages; and the object of the improvement is to produce such surfaces on the dies of the hammer as will result in the blow thereof, when falling on a package of sheets, being distributed uniformly over all parts of the sheets covered thereby. Heretofore it has been the practice to grind or plane such diesto a uniformly flat face when cold. This I have found in practice results, when the dies become hot from use, in the central portion of the face of each die becoming slightly convex by reason of receiving and retaining from the hot packages of sheets a higher degree of heat than the sides and portions nearly adjacent thereto, which in turn results in unequal action of the hammer on different portions of the package.

To the end of affording a remedy for this, my invention consists in giving to the dies, when cold, that degree of concavity which will result in their faces becoming, when at such temperature as they attain in use, true planes, or, what is preferable, in giving to a single one of the dies about twice this degree of concavity.

To carry my invention into effect, I firs have the dies carefully planed, and then examine to ascertain if any concavity has resulted, as is sometimes the case by reason of the central portion of the face being softer than the sides, and causing less springing of the cutting-tool of the planer. Should the concavity so produced chance to exceed the degree hereinafter stated, I correct it by dressing away the rim with a file, and when, as usual, it is less I increase the concavity by further dressing away the central parts of the face with the point of a fiat file or other convenient means.

In practice I prefer to confine the concavity to the lower die, and this should, for a die eighteen (18) inches square and ten (10) inches to twelve (12) inches thick (the common dimensions) be a depression in the center of about one-eightieth of an inch. This I measure by inserting a thin wedgeshaped piece of metal between a straight edge and the face of the die, and ascertain its thickness at the point to which it is admitted by a screw or micrometer-gage. A space of about ten (10) inches square should be reduced to practically the same depression, and thence in each of the four directions slant upward to the level of the edges and attaining this level one-half t) an inch from each edge. Theoretically this should be in a curved line; but the space dealt with being slight, I make the ascent with'as nearly a regular pitch as possible. The dies are now ready for use, and will ordinarily be found after two heats are worked to be sufficiently flat; but if they are not so I strike two or three light blows with the dies naked, and if the upper die is grooved, as is my practice, a discernible print will be left, marking the points of too great fullness, which may then be dressed away. In cases where the dies used are plain I lay a piece of coarse-wire screen on the face of the lower die, and one tap of the hammer will give the indication just described. I find this method of dressing one or both dies to avoid many expensive delays and faults in the finished product.

Having fully described my invention, what I claim, and desire to secure by Letters Patent, 1s

An improvement in hammer-dies for the manufacture of polished sheet-iron, consisting in dressing the face of one or both of the hammer-dies into such degree of concavity when cold as will compensate for their unequal expansion when hot.

\Vitness my hand and seal this 6th day of December, 1888.

ISAAC E. CRAIG. 1,. 8.]

Witnesses:

Y. A. SMITH, J. W. CRUIKSHANK. 

